package com.hadoop;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.util.GenericOptionsParser;

import java.io.IOException;

public class EventCount {

	public static class MyMapper extends Mapper<Object, Text, Text, IntWritable> {

		private final static IntWritable one   = new IntWritable(1);

		private Text					 event = new Text();

		public void map(Object key, Text value, Context context) throws IOException, InterruptedException {
			int idx = value.toString().indexOf(" ");
			if (idx > 0) {
				String e = value.toString().substring(0, idx);
				event.set(e);
				context.write(event, one);
			}
		}
	}

	public static class MyReducer extends Reducer<Text, IntWritable, Text, IntWritable> {

		private IntWritable result = new IntWritable();

		public void reduce(Text key, Iterable<IntWritable> values, Context context)
				throws IOException, InterruptedException {
			int sum = 0;
			for (IntWritable val : values) {
				sum += val.get();
			}
			result.set(sum);
			context.write(key, result);
		}
	}

	public static void main(String[] args) throws Exception {
		Configuration conf = new Configuration();
		String[] otherArgs = new GenericOptionsParser(conf, args).getRemainingArgs();
		if (otherArgs.length < 2) {
			System.err.println("Usage: EventCount <in> <out>");
			System.exit(2);
		}
		Job job = Job.getInstance(conf, "event count");
		job.setJarByClass(EventCount.class);
		job.setMapperClass(MyMapper.class);
		job.setCombinerClass(MyReducer.class);
		job.setReducerClass(MyReducer.class);
		job.setOutputKeyClass(Text.class);
		job.setOutputValueClass(IntWritable.class);
		FileInputFormat.addInputPath(job, new Path(otherArgs[0]));
		FileOutputFormat.setOutputPath(job, new Path(otherArgs[1]));
		System.exit(job.waitForCompletion(true) ? 0 : 1);
	}
}